The pontiff's Vatican security detail received an urgent warning from the British secret services, Francis wrote.

"A woman packed with explosives, a young suicide bomber, was heading towards Mosul to blow herself up during the papal visit," he wrote in "Hope", which goes on sale in over 80 countries in January.

"And a van had also set off at great speed with the same intention," he added, according to excerpts from the book published by the Italian daily Corriere della Sera daily.

The two attackers were intercepted and killed by the Iraqi police.

Francis, who turned 88 on Tuesday, wrote that "almost everyone advised me against" the trip to Iraq "but I wanted to get to the bottom of things. I felt I had to do it".

The historic three-day visit in March 2021 took place amid intense security. It was Francis's first trip in 15 months and took place in the middle of the Covid 19 pandemic.

Despite the high risks to his personal safety, the Argentine pope criss-crossed the country, going to Baghdad and Mosul, the onetime bastion of the Islamic State group.

During his trips abroad, the pope's security is taken care of by the Pontifical Swiss Guard and the Vatican Gendarmerie, in collaboration with local law enforcement.